This pleasant assortment from the magician of math introduces readers to magic squares, the Generalized Ham Sandwich Theorem, origami, electronic roots, an replace of the Induction video game of Eleusis, Dudeney puzzles, the maze at Hampton courtroom palace, and lots of extra mathematical puzzles and ideas.

E. the collection of all the sets which belong simultaneously to all the σ algebras) is again a σ -algebra. It is the smallest σ -algebra containing all intervals and is called the Borel σ -algebra. Roughly speaking, the Borel σ -algebra could be thought of as the collection of sets obtained from intervals by taking countably many unions, intersections and complements. This is a rather rich class of sets which is certainly sufficient for any practical purposes. The elements of the Borel σ -algebra are called Borel sets.